The seismic response of cliff-attached structures under long-period ground motion

Purpose Cliff-attached constructions are buildings directly connected to and aligned with the vertical faces of mountains. They are built on cliffs. Due to their complex grounding relationships, their structural stress and deformation characteristics differ from conventional structures, so the SSI effect must be considered. For a seismic isolation-type structure over a long period, it is especially complicated to consider the SSI (soil-structure interaction) effect, which needs to be explored in depth. On this basis, two structural configurations are established for analysis: the cliff-attached inter-story isolated structure and the double-story isolated structure. A comparison of these arrangements is conducted both with and without considering soil-structure interaction impacts. The extent of the influence of regular earthquakes and far-field and long-period earthquakes on cliff isolation structures is examined under three-dimensional ground motion stimulation. The results suggest that cliff isolation structures react more seismically to far-field and long-period earthquakes than conventional ones. Design/methodology/approach Comparative analysis of these two configurations was subsequently conducted, with and without accounting for soil-structure interaction (SSI) effects. Furthermore, the influence of regular earthquakes versus far-field long-period earthquakes on cliff-attached isolated structures was investigated under three dimensional ground motion excitation. Results show that cliff-attached isolated structures exhibit a more significant seismic response to far-field long-period earthquakes than conventional structures. Findings Particularly evident under three-dimensional ground motion conditions, notably during far-field harmonic-like seismic events, where the response is particularly significant. Under soft soil, far-field non-harmonic and harmonic motions vs ordinary motion cause significant changes: base shear force increases by 31.0 and 38.5%; isolation layer displacement is multiplied by about 2.05/3.18 times (inter-story) and 2.25/3.29 times (double-story). Double-story isolation outperforms seismic response, reducing energy dissipation, enhancing energy dissipation and damping. The SSI effect worsens cliff-attached structures’ seismic response, especially at the structure-mountain interface. 3D far-field motions lead to higher inter-story displacements, with far-field harmonic motions reaching about 2.55/1.56 times that of ordinary/non-harmonic. Soft ground exacerbates this. The compressive stress on isolation bearings in far-field motion is about 2.33/2.45 times that of ordinary ones. Double-story isolation curbs tensile stress, lowers topological risk and shows better stability via full hysteresis and high-energy dissipation. This study can provide some references for the seismic isolation design of cliff-attached structures under long-period earthquakes. Originality/value This paper presents a comprehensive comparative analysis of three-dimensional ground motion dynamics incorporating elastic-plastic behavior and considering the soil-structure interaction (SSI) effect during rare earthquake events. The study encompasses three standard earthquakes and six far-field long-period earthquakes. Specifically, modeling is performed for both cliff-attached inter-story and double-story isolated structures to assess their seismic response. Moreover, the analysis focuses on evaluating the seismic response of cliff-attached structures when subjected to long-period ground motion.